Antibacterial composition

ABSTRACT

An antibacterial composition, and a method for treating infectious diseases by application of the same to animals, comprising a phosphoric acid derivative of the formula ##STR1## where R is lower alkanoyl, and one of nocardicin A, ampicillin, ticarcillin, or cefazolin, or their pharmaceutically acceptable salts. The combination exhibits synergistic antibacterial activity.

The present invention relates to a new antibacterial composition and to a new method for the treatment of infectious diseases caused by pathogenic bacteria. More particularly, it relates to an antibacterial composition comprising a phosphonic acid derivative of the formula: ##STR2## wherein R is lower alkanoyl and

n is an integer of 2 to 5

or its salt and a β-lactam antibiotic or its salt, and to a method for the treatment of infectious disease caused by pathogenic bacteria by application of said antibacterial composition to infected human being or other animals.

As the result of the extensive study of the present inventors, it has been newly found that the phosphonic acid derivative (I) or its salt exhibits a synergistic antibacterial activity by combination with a β-lactam antibiotic such as 1,3-disubstituted azetidinone (e.g. nocardicin A), penicillin or cephalosporin compound, that is, the combination of the phosphonic acid derivative (I) or its salt with the β-lactam antibiotic or its salt shows an effectively stronger antimicrobial activity against the pathogenic bacteria in human being and other animals, against which the phosphonic acid derivative (I) or the β-lactam antibiotic shows no or less antibacterial activity enough to effectively treat human being and other animals for the infectious diseases or to effectively prevent them from said diseases, when each of said compounds is used alone.

Accordingly, an object of the present invention is to provide an antibacterial composition comprising the phosphonic acid derivative (I) or its salt and a β-lactam antibiotic or its salt, which is useful against pathogenic bacteria in human being and other animals, against which each of the phosphonic acid derivative (I), the β-lactam antibiotic and their salts alone is not so effective.

Another object of this invention is to provide a method for the treatment of infectious diseases caused by pathogenic bacteria, which comprises administering the phosphonic acid derivative (I) or its salt in combination with a β-lactam antibiotic or its salt.

These and other objects of the invention will be apparent from the description hereinafter.

The antibacterial composition of the present invention comprises a combination of a phosphonic acid derivative (I) or its salt and a β-lactam antibiotic or its salt.

With regard to the phosphonic acid derivative (I) to be used in this invention, preferred "lower alkanoyl" for R is one having 1 to 6 carbon atoms, among which the most preferred one is formyl and acetyl; and an integer of 3 is most preferred for the symbol "n." That is, the phosphonic acid derivative of the following formula (I') is the most preferred compound to be used in this invention. ##STR3## wherein R' is formyl and acetyl.

The phosphonic acid derivative (I) is an antibiotic having antibacterial activity against various pathogenic bacteria and can be produced by fermentation and/or synthesis, the details of which are described in Belgian Pat. No. 857,211, in which the preferred phosphonic acid derivative (I') can be prepared, for example, by culturing Streptomyces rubellomurinus ATCC 31215 or Streptomyces lavendulae ATCC 31279 in a nutrient medium and recovering the produced 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid or 3-(N-formyl-N-hydroxyamino)propylphosphonic acid from the resultant cultured broth, respectively.

Further, the β-lactam antibiotic to be used in this invention includes 2,3-disubstituted azetidinone, penicillin and cephalosporin compounds, and the preferred β-lactam antibiotic is nocardicin A for 2,3-disubstituted azetidinone, ampicillin and ticarcillin for penicillin, and cefazolin for cephalosporin, which are famous antibiotics described in e.g. THE JOURNAL OF ANTIBIOTICS Vol. 29, pages 492-500 (1976), THE MERCK INDEX NINTH EDITION pages 80 (1976), ANTIMICROBIAL AGENTS AND CHEMOTHERAPY Vol. 7, pages 336-340 (1975), and THE MERCK INDEX NINTH EDITION pages 245 (1976), respectively.

The salts of the above antibiotics, i.e. the phosphonic acid derivative (I), β-lactam antibiotic such as nocardicin A, ampicillin, ticarcillin and cefazolin may include physiologically (e.g. pharmaceutically) acceptable salts such as a metal salt (e.g. sodium, potassium, calcium, barium or magnesium salt), ammonium salt, an amine salt (e.g. ethanolamine, triethylamine, procaine, dibenzylamine or dicyclohexylamine salt) and the like.

From the above description, it is to be noted that the preferred combination of the phosphonic acid derivative and the β-lactam antibiotic is a combination of a phosphonic acid derivative (I') and a β-lactam antibiotic selected from nocardicin A, ampicillin, ticarcillin and cefazolin.

The antibacterial composition of the present invention is useful for treating and preventing diseases induced by pathogenic bacteria in human being and other animals such as poulty, domestic animals, pet animals or experimental animals (e.g. chicken, turkey, duck, quail, cow, cattle, horse, pig, hog, dog, sheep, goat, mink, canary, macaw, mouse, rat or rabbit).

The combination ratio of the phosphonic acid derivative (I) or its salt and the β-lactam antibiotic in the present antibacterial composition may vary depending on the kinds of pathogen and the symptoms of the patients to which the present composition is applied, but may usually be selected within a range of 1:4 to 4:1 by weight, preferably 1:2 to 2:1 by weight and most preferably 1:1.

Further, it is to be noted that the present antibacterial composition may be applied to human being and other animals in conventional forms, examples of which are illustrated as follows.

For applying the present antibacterial composition to human, it is preferable to apply it in the form of intravenous or intramuscular injection. It may also be applied locally in the form of a powder, a suppository or an ointment. When used as an injection, it may be applied in admixture with a solid or liquid carrier or diluent which is usually used for the conventional antibiotic injections, and further, may also be applied together with other medicines such as analgesics (e.g. lidocaine) which are usually used in injections. The most preferred carrier or diluent is water. When used as a suppository and an ointment, it may be used in admixture with conventional suppository and ointment bases, respectively.

For applying the present antibacterial composition to other animals, it is preferable to apply it in the form of injection in the form of infusion. It may also be applied locally in a form of a powder or an ointment. When used as an injection or infusion, it may be applied in admixture with a solid or liquid carrier or diluent which is usually used for the conventional antibiotic injections or infusions. The most preferred carrier or diluent is water, vegitable oils, paraffins or the like. When used as an ointment, it may be applied in admixture with conventional ointment bases.

The dosage of the present antibacterial composition may vary depending on the kinds of the phosphonic acid derivative (I) and the β-lactam antibiotic, the combination ratio thereof and the various factors such as the weight and age of the patient, the kind and severity of the infection, and the kind of the application mode. However, it is to be understood that, as the dosage of the effective ingredient included in the present antibacterial composition, it may be effectively administered to the patient in a dose of about 5 to 200 mg/kg/day, preferably 10-100 mg/day. More particularly, for instance, in the injection to human being, it may be administered in a dose of about 1 to 5 g/day in adults and in a dose of about 10 to 30 mg/kg/day in children, but not limited thereto. For treating bovine mastitis during lactation drying period, it may be administered in a dose of about 50-500 mg/quarter.

And further, it is to be noted that the present antibacterial composition shows low toxicity as shown in the following toxicity test.

Acute Toxicity Test

The acute toxicity test was conducted by using each of the following antibacterial composition according to the following experimental procedure.

(1) Antibacterial composition:

(a) Composition of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A (1:1 by weight).

(b) Composition of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A (1:1 by weight).

(c) Composition of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of ampicillin (1:1 by weight).

(d) Composition of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of cefazolin (1:1 by weight).

(e) Composition of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of ticarcillin (1:1 by weight).

(2) Experimental procedure:

An aqueous solution (0.5 ml) containing one of the above antibacterial composition was intravenously injected into each of three ICR-strain male mice weighing 20 g (Dose:500 mg/kg), respectively. The observation was continued for one week after the administration.

(3) Test results:

All of the test mice were living and normal.

The antibacterial activities and the preventing effectiveness against various bacterial infections of the present antibacterial composition are illustrated by the following experimental tests in vitro and in vivo.

Test 1

Synergistic activity of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and nocardicin A in vitro.

Into a Nutrient broth (Difco) containing prescribed amount of each of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid, monosodium salt of nocardicin A and a mixture of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A (1:1 by weight), there was inoculated overnight-cultured broth of each pathogen in a final concentration of 10⁶ cells/ml, respectively. After the incubation was carried out at 37° C. for 20 hours, Minimum Inhibitory Concentration (MIC) values were determined, respectively.

Further, in order to observe the degree of synergistic antimicrobial activity, Fractional Inhibitory Concentration (FIC) values and FIC Index were calculated from the determined MIC values according to the following calculation method, respectively.

Calculation Method

(a) MIC value of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid: Ao

(b) MIC value of monosodium salt of nocardicin A: Bo

(c) MIC value of a mixture of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A: Cab

On the basis of the fact that the combination ratio of a mixture of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A is 1:1 (by weight), each of FIC values and FIC indexes was calculated according to the following equations.

FIC of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid=1/2Cab/Ao.

FIC of monosodium salt of nocardicin A=1/2Cab/Bo.

FIC index=(1/2Cab/Ao)+(1/2Cab/Bo).

The test results are shown in the following table.

                                      Table 1.                                     __________________________________________________________________________     Synergism between 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid             and nocardicin A against pathogenic bacteria                                                 MIC (mcg/ml)                                                                               FIC      FIC                                         Microorganism                                                                          strain No.                                                                           A    B  C   A    B   index                                       __________________________________________________________________________             1101-63                                                                              800  400                                                                               100 0.063                                                                               0.125                                                                              0.188                                       Pseudomonas                                                                            1101-64                                                                              >800 200                                                                               50  <0.031                                                                              0.125                                                                              <0.156                                      aeruginosa                                                                             1101-66                                                                              200  100                                                                               50  0.125                                                                               0.250                                                                              0.375                                               1101-67                                                                              200  200                                                                               100 0.250                                                                               0.250                                                                              0.500                                               1101-68                                                                              800  100                                                                               50  0.031                                                                               0.250                                                                              0.281                                       Escherichia                                                                            1341-27                                                                              200  100                                                                               50  0.125                                                                               0.250                                                                              0.375                                       coli    1341-35                                                                              100  100                                                                               50  0.250                                                                               0.250                                                                              0.500                                       Klebsiella                                                                             1391-1                                                                               400  800                                                                               100 0.125                                                                               0.063                                                                              0.188                                       pneumoniae                                                                             1391-2                                                                               >800 800                                                                               400 <0.250                                                                              0.250                                                                              <0.500                                              1391-3                                                                               800  800                                                                               400 0.2650                                                                              0.250                                                                              0.500                                               1391-5                                                                               400  800                                                                               200 0.250                                                                               0.125                                                                              0.375                                       Serratia                                                                               1421-1                                                                               >800 100                                                                               12.5                                                                               <0.008                                                                              0.063                                                                              <0.071                                      marcescens                                                                             1421-3                                                                               >800 400                                                                               100 <0.063                                                                              0.125                                                                              <0.188                                              1421-4                                                                               >800 400                                                                               50  <0.031                                                                              0.063                                                                              <0.094                                              1421-5                                                                               >800 200                                                                               25  <0.016                                                                              0.063                                                                              <0.079                                      __________________________________________________________________________      Note                                                                           A: Monosodium salt of 3(N-acetyl-N-hydroxyamino)propylphosphonic acid.         B: Monosodium salt of nocardicin A.                                            C: A mixture of monosodium salt of                                             3(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of         nocardicn A (1:1 by weight).                                             

Test 2

Synergistic activity of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and ampicillin in vitro:

On a Nutrient agar (Difco) containing prescribed amount of each of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid, monosodium salt of ampicillin and a mixture of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of ampicillin (1:1 by weight), there was streaked a loopful of cultured broth of each pathogen, which was cultured overnight in Nutrient broth (Difco), in a concentration of 10⁵ cells/ml. After the incubation was carried out at 37° C. for 20 hours, MIC values were determined.

FIC values and FIC Index were calculated in substantially the same manner as described in Test 1.

The test results are shown in the following table.

                  Table 2                                                          ______________________________________                                         Synergism between 3-(N-formyl-N-hydroxyamino)propyl-                           phosphonic acid and ampicillin against pathogenic bacteria                                     MIC (mcg/ml)  FIC                                              Microorganism     A         B      C    index                                  ______________________________________                                         Staphylococcus epidermidis 1601-1                                                                ≧400                                                                              0.2    0.2  0.5                                    Klebsiella pneumoniae NCTC 418                                                                   25        12.5   3.13 0.2                                    Shigella flexneri Ia EW-8                                                                        1.56      0.78   0.78 0.8                                    Salmonella enteritidis 1891                                                                      0.78      0.39   0.39 0.8                                    Salmonella typhimurium 1406                                                                      6.25      0.39   0.39 0.5                                    Salmonella paratyphi A-1015                                                                      6.25      0.39   0.39 0.5                                    Serratia marcescens 1421-4                                                                       50        25     3.13 0.1                                    Enterobacter aerogenes 1402-10                                                                   6.25      200    3.13 0.3                                    Enterobacter cloacae 1401-4                                                                      3.13      100    3.13 0.5                                    Alcaligenes faecalis 1311-1                                                                      ≧400                                                                              6.25   6.25 0.5                                    Proteus mirabilis 1432-75                                                                        1.56      0.39   0.2  0.3                                    Proteus vulgaris IAM-1025                                                                        1.56      0.78   0.78 0.8                                    Proteus morganii 1433-2                                                                          ≧400                                                                              25     25   0.5                                     Note                                                                           A: Monosodium salt of 3(N-formyl-N-hydroxyamino)propylphosphonic acid.         B: Monosodium salt of ampicillin                                               C: A mixture of monosodium salt of                                             3(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of         ampicillin (1:1 by weight).                                              

Test 3

Synergistic activity of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and cefazolin; that of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid and ticarcillin; and that of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid an nocardicin A were tested in vitro in substantially the same manner as described in the above Test 2.

The test results are shown in the following Table 3, 4 and 5, respectively.

                  Table 3.                                                         ______________________________________                                         Synergism between 3-(N-formyl-N-hydroxyamino)propyl-                           phosphonic acid and cefazolin against pathogenic bacteria                                      MIC (mcg/ml) FIC                                               Microorganism     A       B       C    index                                   ______________________________________                                         Staphylococcus epidermides 1601-1                                                                ≧400                                                                            0.39    0.39 0.5                                     Escherichia coli 1341-18R.sup.+                                                                  6.25    3.13    1.56 0.4                                     Klebsiella pneumoniae NCTC 418                                                                   25      1.56    1.56 0.5                                     Serratia marcescens 1421-4                                                                       50      400     25   0.3                                     Enterobacter aerogenes 1402-10                                                                   6.25    12.5    3.13 0.4                                     Enterobacter cloacae 1401-4                                                                      3.13    ≧400                                                                            3.13 0.5                                     Proteus rettgeri 1434-3                                                                          1.56    6.25    1.56 0.6                                     Proteus morganii 1433-2                                                                          ≧400                                                                            25      25   0.5                                     Pseudomonas aeruginosa 1101-76                                                                   1.56    ≧400                                                                            1.56 0.5                                     ______________________________________                                          Note                                                                           A: Monosodium salt of 3(N-formyl-N-hydroxyamino)propylphosphonic acid.         B: Monosodium salt of cefazolin.                                               C: A mixture of monosodium salt of                                             3(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of         cefazolin (1:1 by weight).                                               

                  Table 4.                                                         ______________________________________                                         Synergism between 3-(N-formyl-N-hydroxyamino)propyl-                           phosphonic acid and ticarcillin against pathogenic bacteria                                    MIC (mcg/ml) FIC                                               Microorganism     A         B      C    index                                  ______________________________________                                         Staphylococcus epidermides 1601-1                                                                ≧400                                                                              3.13   3.13 0.5                                    Klebsiella pneumoniae NCTC418                                                                    25        100    25   0.6                                    Salmonella typhimurium 1406                                                                      6.25      1.56   1.56 0.6                                    Serratia marcescens 1421-4                                                                       50        25     12.5 0.4                                    Enterobacter cloacae 1401-4                                                                      3.13      50     3.13 0.5                                    Proteus mirabilis 1432-75                                                                        1.56      0.78   0.78 0.8                                    ______________________________________                                          Note                                                                           A: Monosodium salt of 3(N-formyl-N-hydroxyamino)propylphosphonic acid          B: Monosodium salt of ticarcillin                                              C: A mixture of monosodium salt of                                             3(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of         ticarcillin (1:1 by weight)                                              

                  Table 5.                                                         ______________________________________                                         Synergism between 3-(N-formyl-N-hydroxyamino)-                                 propylphosphonic acid and nocardicin A against pathogenic                      bacteria                                                                                        MIC (mcg/ml)                                                                               FIC                                               Microorganism      A      B       C    index                                   ______________________________________                                         Klebsiella pneumoniae NCTC418                                                                     25     200     25   0.6                                     Salmonella typhimurium 1406                                                                       6.25   25      6.25 0.6                                     Serratia marcescens 1421-4                                                                        50     25      6.25 0.2                                     Proteus mirabilis 1432-75                                                                         1.56   3.13    0.78 0.4                                     ______________________________________                                          Note                                                                           A: Monosodium salt of 3(N-formyl-N-hydroxyamino)propylphosphonic acid          B: Monosodium salt of nocardicin A                                             C: A mixture of monosodium salt of                                             3(N-formyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of         nocardicin A (1:1 by weight)                                             

As seen clearly from the above results in Test 1-5, the combination of the phosphonic acid derivative (I) and a β-lactam antibiotic selected from nocardicin A, ampicillin, ticarcillin and cefazolin shows synergistic antibacterial activity against various pathogens.

Test 4

Effects on the experimentally infected mice:

ICR-strain male mice weighing 23-25 g (10 mice per one group) were used. A prescribed amount of the pathogenic bacteria suspended in 5% aqueous mucin suspension (0.5 ml.) was inoculated intraperitoneally into each mouse. One hour after the inoculation, the antibiotics as mentioned in the following table were administered subcutaneously, and then survival of the test mice was measured one week after the infection to determine ED₅₀ value. The results are shown in the following Table 6.

Incidentally, FIC values and FIC index in this in vivo test were also calculated from the determined ED₅₀ values according to the following calculation method.

Calculation Method

(a) ED₅₀ value of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid: A'o

(b) ED₅₀ value of monosodium salt of nocardicin A:B'o

(c) ED₅₀ value of a mixture of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A: C'ab

On the basis of the fact that the combination ratio of a mixture of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of nocardicin A is 1:1 (by weight), each of FIC values and FIC index was calculated according to the following equations.

FIC of monosodium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid=1/2C'ab/A'o

FIC of monosodium salt of nocardicin A=1/2C'ab/B'o

FIC index=(1/2C'ab/A'o)+(1/2C'ab/B'o)

                  Table 6.                                                         ______________________________________                                         Synergism between 3-(N-acetyl-N-hydroxyamino)propylphosphonic                  acid and nocardicin A in protecting activity                                   Microor-                                                                               strain   ED.sub.50 (mg/mouse)                                                                        FIC      FIC                                     ganism  No.      A      B    C    A     B    index                             ______________________________________                                         Pseudomonas                                                                            1101-5   >20     1.3 0.71 <0.018                                                                               0.273                                                                               <0.291                            aeruginosa                                                                             1101-7   >20    15.0 2.5  <0.063                                                                               0.083                                                                               <0.146                            ______________________________________                                          Note                                                                           A: Monosodium salt of 3(N-acetyl-N-hydroxyamino)propylphosphonic acid          B: Monosodium salt of nocardicin A                                             C: A mixture of monosodium salt of                                             3(N-acetyl-N-hydroxyamino)propylphosphonic acid and monosodium salt of         nocardicin A (1:1 by weight)                                             

As seen clearly from the above results, the synergistic antibacterial activity of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and nocardicin A was also confirmed by in vivo test.

The antibacterial compositions of the present invention are illustrated by the following Examples.

EXAMPLE 1

A sterile mixture of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid (125 mg) and monosodium salt of nocardicin A (125 mg) was put in a sterile vial and the vial was sealed. And when used, the above mixture was dissolved in a sterile water (2 ml.) to give an injection preparation.

In substantially the same manner as described in the above Example 1, there was prepared an injection preparation of an antimicrobial composition as illustrated in the following Examples 2-5.

EXAMPLE 2

A mixture of monoammonium salt of 3-(N-acetyl-N-hydroxyamino)propylphosphonic acid (250 mg.) and monosodium salt of nocardicin A (125 mg.) was used as the active ingredient for injection.

EXAMPLE 3

A mixture of monopotassium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid (250 mg.) and monosodium salt of ampicillin (250 mg.) was used as the active ingredient for injection.

EXAMPLE 4

A mixture of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid (125 mg.) and monosodium salt of cefazolin (125 mg.) was used as the active ingredient for injection.

EXAMPLE 5

A mixture of monosodium salt of 3-(N-formyl-N-hydroxyamino)propylphosphonic acid (250 mg.) and monosodium salt of ticarcillin (250 mg.) was used as the active ingredient for injection. 

What is claimed is:
 1. An antibacterial composition containing a mixture comprising a phosphonic acid derivative of the formula: ##STR4## wherein R' is formyl or acetyl, or its pharmaceutically acceptable salt and nocardicin A or its pharmaceutically acceptable salt, the proportions of the phosphonic acid derivative or its pharmaceutically acceptable salt to the nocardicin A or its pharmaceutically acceptable salt being in the range of 1:2 to 2:1 by weight.
 2. A method of treating an infectious disease caused by a pathogenic bacteria in humans and animals, which comprises administering to said human or animal an effective amount of the antibacterial composition of claim 1, in a pharmaceutically acceptable carrier.
 3. A method of treating an infectious disease caused by a pathogenic bacteria in humans and animals, which comprises intravenously or intramuscularly administrating to said human or animal a daily dose of 10 to 100 mg/kg, as effective ingredient of the antibacterial composition of claim 1, in a pharmaceutically acceptable carrier.
 4. An antibacterial composition containing a mixture comprising (I) 3-(N-formyl-N-hydroxyamino) propylphosphonic acid or its pharmaceutically acceptable salt and (II) nocardicin A or its pharmaceutically acceptable sale, the proportions of (I) to (II) being 1:1 by weight, in a pharmaceutically acceptable carrier.
 5. An antibacterial composition containing a mixture comprising (I) 3-(N-acetyl-N-hydroxyamino) propylphosphonic acid or its pharmaceutically acceptable salt and (II) nocardicin A or its pharmaceutically acceptable salt, the proportions of (I) to (II) being 1:1 by weight, in a pharmaceutically acceptable carrier.
 6. An antibacterial composition according to claim 4 in which compound (I) is the monosodium salt of 3-(N-formyl-N-hydroxyamino) propylphosphonic acid and component (II) is the monosodium salt of nocardicin A.
 7. An antibacterial composition according to claim 5 in which component (I) is the monosodium salt of (3-(N-acetyl-N-hydroxyamino)propylphosphonic acid and component (II) is the monosodium salt of nocardicin A. 